In many fluid systems, fluids of different specific gravity collect. It is sometimes desirable to bleed a fluid of a first, lower, specific gravity from a fluid of a second, higher, specific gravity, from the fluid system. Many fluid systems are for managing air in a liquid system, where the air is a fluid of lower, specific gravity and the liquid is a fluid of higher, specific gravity. A typical example would be separating air from a hydraulic fluid or similar liquid.
Many bleed valve arrangements are designed to manage the amount of air present in a liquid system. For example, air bleed valves are used in pressurized liquid systems such as hydraulic systems to remove unwanted air. Air presence in such systems is detrimental because it can cause cavitation in pumps, oxidation, foaming, and/or reduced bulk modulus. Example bleed valves are shown in U.S. Pat. Nos. 8,833,695 and 8,272,398. The complete disclosures of these references are incorporated herein by reference.
An example bleed valve assembly 10 is depicted in FIG. 1. This bleed valve assembly 10 includes a housing 12, a liquid level sensor 14, a solenoid valve 16, and a bleed chamber 18. The housing 12 includes an inlet port 20.
In use, this bleed valve assembly 10 would be mounted in flow communication with an appropriate, typically upper, portion of a tank of a fluid system, typically under pressure (for example a hydraulic system, not shown) to receive liquid flow from the fluid system through the port 20. Over time, air trapped in the fluid system would also enter the bleed valve assembly 10 through the port 20 and into the bleed chamber 18. The function of the bleed valve assembly 10 is to selectively bleed this air from the fluid system with minimal discharge of the liquid.
The liquid level sensor 14 is configured to detect when the liquid in the bleed chamber 18 has fallen below a pre-determined level, thus indicating an amount of excess air has been collected in the system that needs to be bled therefrom. The liquid level sensor 14 can be an optical sensor, or a contact sensor, for example. When the liquid level sensor 14 no longer detects the designated or selected liquid level, it sends a signal, for example through an electronic control mechanism 22, to the solenoid valve 16 to open and allow the excess air to vent from the bleed valve assembly 10, for example, to the atmosphere.
In particular, an air bleed conduit 24 is in fluid communication with the bleed chamber 18 and the solenoid valve 16. The air bleed conduit 24 allows excess air to vent from the bleed chamber 18 through outlet 26 and valve seat 28 when the solenoid valve 16 is actuated, to open the valve seat 28 to allow air flow therethrough, by movement of valve member 30 from the valve seat 28 in response to the signal from the liquid level sensor 14. The solenoid valve 16 closes (for example under spring pressure) once the liquid level rises sufficiently (i.e., after bleed). Because the hydraulic system is under internal pressure, the excess air is readily forced from the bleed chamber 18 and the bleed valve assembly 10 when the valve seat 28 opens.
Typically, the housing 12 is configured and positioned in use, such that a mounting axis 32 thereof extends horizontally or coaxially with the port 20. This keeps air above the liquid detection level in the bleed chamber 18 and below the air bleed conduit 24 as air enters the hydraulic system.
The bleed valve 10 includes a plug 34 to ensure the flow of excess air is directed through outlet 26 and the valve seat 28.
Improvements in bleed valves relating to assembly and use, are desirable.